Molecular systematics and phylogeography of neotropical grasshoppers in the genus Sphenarium (Orthoptera: Pyrgomorphidae)

Multiple phylogeographic studies in Mexico suggest that during the last 23 million years formation of Transmexican Volcanic Belt, inundation of the Isthmus of Tehuantepec and climatic fluctuations related to Pleistocene’s glacial and interglacial cycles caused diversification of several vertebrate and plant taxa. Phylogenetic and phylogeographic studies in arthropods can help to understand the impact that major geologic and climatic events could have in biotic diversification in Mexico. However, relatively little is know about the time and patterns of diversification of arthropods in central and southern Mexico. The grasshopper species in the genus Sphenarium show biological, ecological and biogeographic characteristics that make them an adequate system for exploring the effects those historical events could had on diversification of neotropical insects in Mexico. This study aims to evaluate if patterns and time of diversification of the genus Sphenarium is related to neogenic geologic and quaternary climatic events. We expect that low land species represent older linages than those distributed in high lands, and that phylogenetic relationships and inter-specific divergence time reflect the sequence of past geologic and climatic events. Finally we expect to find genetic intra-specific evidence of past population isolation and reduction in those species whose divergence is associated with Quaternary climatic fluctuations. We used mitochondrial and nuclear genetic variation to infer phylogenetic relationships and to estimate divergence time among the species. Preliminary data gives support to the hypothesis proposed.